It is a shrine to Hollywood's elite and it comes with all the trappings -- music, sound bites, high fashion, paparazzi, applause, a red carpet and Joan Rivers.

Comedienne Joan Rivers is a friend who was invited to the official Buckingham Palace birthday party on Wednesday.

Much of the interview was serious, although Letterman kicked off with a series of quips about the level of security needed, which he described as "tighter than Joan Rivers' face".